Does changing the fps change the speed of the animation?
Generally, the keyframes (as the name indicates) of blender animations are based on frame numbers instead of absolute time. So if you render an animation that has been created with 30fps in mind at 60 fps, the video will be half the length.
If you really want it to be 60 fps and you do not want to redo the whole animation, you could make use of the &quot;time remapping&quot; parameter (https://docs.blender.org/manual/en/latest/render/output/settings.html), as described here for example: How to render an animation at a higher framerate?